Is it possible to animate 2 separate objects with 1 action animation?
Okay so after much trial and error, it seems that the only possible way to do this is with an armature. Just rig the armature to all the objects you want to animate and create one action animation in the armature. I have 4 bones in the armature, none of which are actually connected with each other (both the bones and the objects) and I just animate the bones. ! animation to export to Unity with many different moving parts.